Ready Mixed Concrete (RMC)
Ready mixed concrete (RMC) is a concrete, delivered at site or into the purchaser's vehicle, in plastic condition and requires no further treatment before being placed in a position in which it is to set and harden. It is a high quality concrete of required grade produced under strictly controlled conditions in a centralised automatic batching plant and supplied to the customer in a transit mixer truck for its placement at site. The concrete can be mixed either dry at the batching plant, loaded into agitator truck mixers and water added during transportation; or it
can be mixed wet at the batching plant, discharged into the agitator truck mixers and transported
to site. The first RMC plant was established in the year 1992 in Pune. At present, RMC plants
are located in almost all the cities of India
Admixtures of RMC
Generally RMC is transported to sites which are located at long distances from the batching plants. At the delivery point, concrete should be workable and plastic. The transit period is sometimes four to five hours. The ordinary concrete will suffer slump loss due to the time lost in transit and evaporation of water due to atmospheric conditions such as high temperature. Therefore, admixtures will be required to extend the setting time and, retention of specified slump of concrete. Superplasticizers are, therefore, used to assure quality, workability, and strength of ready mixed concrete. Two types of admixtures are in use-the high performance water reducing admixtures and a high range water-reducing super-plasticizers. High performance water reducing admixtures have been specially designed to retain workability even in high ambient temperature. The examples are conplast RMC P 333 and conplast RMC P 505. The advantages of using high performance water reducing admixtures are:
1. Improved cohesion and reduced bleeding and segregation.
2. Makes the mix cohesive even if the aggregates are of slightly poor grading.
3. Since chloride free it is safe for use in reinforced and prestressed concrete.
4. Improved workability and workability retention with controlled extended setting time and hence ideal for use in hot weather condition.
5. Workability increases without extra water addition.
6. Assists in producing dense, close textured, low permeability concrete thus enhancing durability.
7. Water reduction helps in improvement of compressive strength at all ages.
Advantages of RMC
1. Enhanced quality and durability resulting in lower maintenance costs and increased speed of construction.
2. Ready mix concrete is consistently of the same quality and provides a high quality of construction material; construction time is also reduced.
3. It reduces congestion at the site and prevents traffic jams.
4. It hastens infrastructure development and thus provides more employment opportunities.
5. It is an environmentally safer alternative.
6. With ready mixed concrete, modern construction techniques can be followed.
Convenience-Ready Mix Concrete is delivered at the site with minimum logistical hassles.
8. Different types of concretes can be made for different applications.
9. Use of RMC obviates the need to set up the infrastructure required for site manufactures
of concrete. This also reduces the working capital to be invested by the customers, as they
will not be required to maintain stock of aggregates, cement, plant and machinery etc.
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